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Open-Source Vulnerabilities Paint A Target On Android
With smartphone exploits on the rise, an almost-successful attack against Android devices hints at future dangers
In 2009, Red Hat, SuSE, and other Linux distributors fixed a major flaw that could have allowed any user to escalate his privileges and fully compromise a Linux system. The vulnerability, in theudev process, occurred because the device-resource-handling component did not verify that a certain type of message, known as a netlink message, came from the kernel.
A variant of the udev flaw, or CVE-2009-1185, is one component of the DroidDream attack identified earlier this month. That exploit, called exploid.c, uses a netlink message to create a user-controlled copy of the init process, which handles boot up, thus gaining root access. The init process reuses much of the code from the previously vulnerable udev process, according to Zach Lanier, a security consultant with mobile-security provider Intrepidus Group.
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"Large chunks of code have been moved from udev to the init daemon," Lanier says. "The exploit uses the same technique but attacks a different process."
The DroidDream attack used the init process flaw and another vulnerability -- a resource exhaustion attack on the Android debugging bridge (adb) -- to install a rootkit that could install additional malicious software from a command-and-control server. However, the attack never matured to that point before the 58 infected apps were removed from the Android Marketplace, and Google used its capability to remotely remove the application from nearly 260,000 victims' phones.
Yet such an attack will undoubtedly happen again. The openness of the Android operating system and the fact that it is based on Linux means that a large cadre of operating-system hackers can attempt to find vulnerabilities in the system. And they have an incentive to do so: While cybercriminals typically target PCs with malware to make money, many of the exploits created for smartphones are motivated by the need to jailbreak the devices to gain certain functionality, such as the ability to switch cellular providers.
"The place where we are seeing mature, reliable exploit code being disseminated are for vulnerabilities that people are using to rootkit or jailbreak their phones," says Tom Cross, a security researcher with IBM's Internet Security Systems' X-Force research team. "Obviously, there is a desire to do that to these devices and that is driving the creation of these reliable exploits, and those exploits can be used for malicious purposes."
IBM has tracked smartphone exploits and found that attacks have steadily increased during the past few years.
Moreover, as demonstrated by the DroidDream incident, carriers and manufacturers tend to be slow to patch their phones, leaving them vulnerable longer. At least 42 percent of Android-based phone used vulnerable versions of the operating system -- version 2.1 and below, according to the Android developer site. In reality, Android 2.2.1 and below are vulnerable, but it's uncertain what fraction of the 58 percent of phones running Android 2.2 are running a vulnerable version.
It's no mystery as to why: The pipeline for fixing vulnerabilities is more tortuous than in the computer industry. After a patch is accepted, Google must commit the fix to the code base, the manufacturer must produce a tailored build of the operating system for its products and test the software, and, finally, the carrier has to test the software on its own network and then push out an over-the-air update.
"The Linux kernel might be updated, but there is still a window in which it has to be pushed into the Android tree, then pushed into a OEM's build ... then pushed into the carrier's queue to be updated," Lanier says. "So you are talking months between when a kernel-level bug is found and the patch on mainstream Linux distributions and finally rolled out to the Android devices."
Still, like the DroidDream incident, smartphones do have significant security controls in place, so it's uncertain how successful attacks will be against the platforms. Apple patches the iPhone on par with PC-industry norms, and its control of the App Store means that attackers have a hard time getting malicious code onto victims' phones. Similarly, Google's control over the Android Marketplace allows it to respond quickly to outbreaks and limit the spread of malicious code. Both benefit from the security controls in Linux and some form of sandboxing.
"These platforms are getting more robust," Lanier says. "If used right, you know, in the ideal world of unicorns and gumdrops, the security model of Android is fairly robust."
Moreover, the latest incident might have been a watershed for mobile malware, but the easiest and most sure way to steal data remains to steal the phone, not compromise it with malware, IBM's Cross says.
"Right now that approach is not proven as a successful way to steal data from people," Cross says. "So there is still the question is what is the criminals business model that leads to widespread exploitation ... so far, none has arisen."
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